1. Field of the Invention
This invention relates to an apparatus for breaking one or more objects into a plurality of smaller objects.
2. Related Art
There are a large number of situations in which it is desired to break one or more objects into a plurality of smaller objects. For instance, in mining, it is frequently necessary to break pieces of ore into smaller pieces of ore. In the production of feed from, for example, corn, it is necessary to break kernels of corn into smaller pieces. In glass recycling, it is necessary to break bottles or other relatively large pieces of glass into smaller pieces of glass.
One means to break a plurality of objects into smaller objects is a mill. Typically, a mill comprises a chamber (having inlet and outlet ports) in which the objects are crushed, and a crushing means inside the chamber which collides with the objects to break them into smaller objects. Often, the crushing means comprises one or more hammers which are attached to and rotated by a shaft within the chamber such that the hammers smash the objects against raised surfaces (lands) formed on the chamber walls. The shaft can be either vertical or horizontal. The inlet port is typically formed in either the side or the top of the chamber. The outlet port is typically formed in either the top or bottom of the chamber.
In mills in which objects are broken into smaller objects by collision with parts of the mill (i.e., the crushing means and interior walls of the chamber), it is difficult to achieve a very small size of the discharged objects. Further, insofar as small-sized discharged objects can be produced, existing mills require a long time (hours or days) to achieve the small sizes.
In one type of mill, known as a gravity discharge mill, discharge of the crushed objects from the chamber is accomplished by gravity. Objects to be crushed are fed into the chamber through the inlet port which is formed in either the top or side of the chamber. The objects are crushed until they drop out of the outlet port formed near the bottom of the chamber. In gravity discharge mills, uniformity in size of discharged objects is poor since objects are discharged haphazardly (i.e., whenever an object happens to fall out of the outlet port), rather than according to size.
In another type of mill, the outlet port is located in the top of the chamber. The objects to be crushed are typically fed into the chamber through an inlet port formed in the side of the chamber. The objects are crushed until an impact within the chamber propels them out of the outlet port. Again, however, poor size uniformity is a problem with such mills, since objects are discharged from the chamber not according to size, but rather as matter of happenstance (i.e., when an impact propels an object in the proper direction).
In mills having the outlet port formed in either the bottom or top of the chamber, objects introduced into the chamber do not have to pass all the way across the chamber (in the horizontal direction) before being discharged. Therefore, it is difficult to efficiently crush objects into very small sizes since the objects may spend a relatively small amount of time in the chamber and receive a relatively small number of impacts.